As the manufacture and production of goods has become more automated, it has become increasingly desirable to automate other facets of the production of goods, especially the packaging of goods. One particular area of interest has been in the packaging of goods in cartons such as the packaging of soft drink cans or bottles, etc., in cardboard cartons, such as for beverage "twelve-packs". As a part of an automated packaging operation, the cartons generally are selected from a stack of cartons in which the cartons are stacked one on top of another in a substantially flat orientation. The cartons are pulled from the stack and transferred to a transport conveyor. Along the way, the cartons must be spread apart into an opened position prior to placement within the carton pockets of the transport conveyor. The transport conveyor carries the opened cartons to a packaging station wherein the opened cartons are packed with products such as cans of soft drinks, etc.
The principal problem encountered in transferring cartons from a flat stacked arrangement to the carton pockets of the conveyor has been in accomplishing the steps of selecting, opening and loading the cartons in as expediently and efficiently a manner as possible. In the past, conventional carton transfer assemblies generally have used a series of vacuum cups mounted on a rotating frame. The vacuum cups are rotated into engagement with a substantially vertically oriented stack of cartons and apply a suction force or vacuum against adjacent panels of the cartons to pull the cartons from the stack. These prior art carton transfer assemblies further typically include stabilizing members, known as "stingers" that engage rear panels of the cartons during the transfer process. The stingers tend to urge the rear panels of the cartons away from the carton front panels to cause the cartons to be spread apart into an opened arrangement.
For example, U.S. Pat. Nos. 5,105,931 of Lashyro and 5,019,029 of Calvert both disclose carton transfer or control assemblies that include suction or vacuum cups that engage and pickup collapsed sleeve type cartons from a flat stack of cartons. The vacuum cups transfer the cartons to a transport conveyor in which the cartons are loaded in an opened, spread apart configuration. Lashyro further discloses the use of stabilizing members or stingers that are received through and engage the cartons at cutouts in the front panels thereof to spread apart the panels of the carton and open the carton.
Problems arise, however, with the use of conventional stingers for spreading and opening the cartons during a transfer operation. As illustrated in the Lashyro, U.S. Pat. No. 5,105,931, most conventional stingers typically comprise spring-biased rods or pins mounted adjacent the vacuum cups of the system. The springs bias the stingers into engagement with the rear panels of the cartons to spread the panels of the cartons to open the cartons. Conventional article transfer assemblies generally have relied upon the stingers being moved against the force of their springs into a retracted position by the weight of the carton stack as the vacuum cups are moved into engagement therewith. Thereafter, the force of the vacuum being pulled through the vacuum cups against the panels of the cartons has been used to pull against the force of the springs to maintain the stingers in their retracted, out of the way positions.
A problem, however, arises when the stack of cartons gradually is lessened by the removal of cartons therefrom, which reduces the weight of the carton stack. As the weight of the carton stack is decreased, the biasing force of the springs of the stingers no longer is overcome by the weight of the stack, but instead the stacked cartons tend to be pushed away from the vacuum cups by the extended stingers. As a result, the vacuum cups miss picking or engaging the cartons, or only partially engage the cartons so that the transfer and loading operation is disrupted and/or the cartons are damaged. Additionally, the length of most conventional stingers generally has been limited in order to avoid engagement with the panels of the cartons during the picking of the cartons from the stack and the unloading of the opened cartons into the carton pockets of the conveyors. Such engagement can tear and/or cause damage to the panels of the cartons, requiring the cartons to be discarded.
These problems are magnified as the speed of the carton transfer assembly is increased. Accordingly, the rate of transfer of cartons from a flat stacked arrangement into an opened configuration positioned within the carton pockets of a transport conveyor generally has been limited with conventional transfer systems, and such systems typically have had to be constantly and carefully monitored to ensure their proper and efficient functioning.
Accordingly, it can be seen that a need exists for a carton transfer assembly for transferring canons from a flat stacked arrangement to a transfer conveyor which includes stingers for engaging, urging and spreading apart the panels of the cartons to open the carton in which the stingers are automatically retracted as the cartons are picked up and loaded into the carton pockets of a transport conveyor so as to minimize the danger of the panels of the canons being engaged and damaged by the stingers and to avoid the mispicking of the cartons by the vacuum engagement cups to enable the faster and more efficient transfer of the cartons.